1. Field of the Invention
The present invention relates to an automatically identifying decode apparatus for automatically identifying and decoding digital data of various types pertaining to a plurality of different systems. In particular, the present invention relates to an automatically identifying decode apparatus for enhancing the speed of a process of decoding digital data.
2. Description of the Related Art
So far, an information processing system for handling mixed data having a variety of types pertaining to a plurality of different systems has been proposed. Examples of bar-code systems for handling bar codes as digital data include JAN, C39, NW7 and ITF. There are a plurality of bar-code systems which are different from each other depending upon the application fields of the bar codes. In such systems, an automatically identifying decode apparatus, which can identify the type of digital data automatically and decode the digital data of whatever type, is employed.
A typical automatically identifying decode apparatus employed in an information processing system for handling such kinds of bar codes is disclosed in the U.S. Pat. No. 4,743,744. An overview of the automatically identifying decode apparatus is described as follows.
The automatically identifying decode apparatus employes a bar-code scanner having a bar-code reader for reading a bar code. A signal generated by the bar-code reader is converted into a binary-code signal which conveys count values each representing the width of a bar of the bar code. The count values are added up to give a total which is stored into a count-value memory unit 71. That is to say, as the operation to read the bar code is completed, a total count value N representing a total width of all bars is stored into the count-value memory unit 71. A read start signal SR is supplied to a read start signal input terminal 79 to read the count values N from the count-value memory unit 71 one after another in the same order they were stored in the memory unit 71. Data read from the count-value memory unit 71 is supplied to bar-code decoders 72, 73 and 74.
The bar-code decoder 72, a bar-code decoder for the JAN system, is requested by the read start signal SR to decode the count value N. Assume that the count value N representing a JAN bar code is decoded by the bar-code decoder 72 successfully into decoded data DD. In this case, a decode completion signal E1 is output at the end of the decoding to indicate a successful operation.
A count value N not representing a JAN bar code, on the other hand, cannot be decoded by the bar-code decoder 72 which is dedicated only for the JAN system. In this case, a decode failure signal F1 is output along with the decode completion signal E1. Both the signals E1 and F1 are supplied to an AND gate 75 to produce an error signal ER1 which is fed to the count-value memory unit 71 as an activation signal through an OR gate 78, and to the bar-code decoder 73 for the ITF system.
The activation signal activates an operation for reading the count value N from the count-value memory unit 71 again. This time, however, the count value N is decoded by the bar-code decoder 73 for the ITF system. Much like the bar-code decoder 72, decoded data DD and a decode completion signal E2 are output for a successful operation. If decoding cannot be performed, however, the decode completion signal E2 and a decode failure signal F2 are both supplied to an AND gate 76 to generate an error signal ER2. The error signal ER2 is fed to the count-value memory unit 71 as an activation signal through an OR gate 78, and to the bar-code decoder 74 for the NW7 system. Likewise, the bar-code decoder 74 makes an attempt to decode the count value N again.
As described above, the automatically identifying decode apparatus for decoding a bar code once stores a count value N representing the widths of bars of a bar code into a count-value memory unit 71. The stored count value N is then supplied to the bar-code decoders 72, 73 and 74 in turn, to one bar-code decoder at a time, for decoding. Thus, at least, while a count value N is being written into the count-value memory unit 71, no decoding operation can be performed. In other words, a decoding operation cannot be started until the operation to write a count value N into the count-value memory unit 71 is completed. As a result, it takes a long time to complete the decoding of a count value N read from a bar code.
In addition, it is necessary to store all count values resulting from an operation to read bar-code data in the count-value memory unit 71. Therefore, a RAM (Random-Access Memory) unit with a large capacity is used as the count-value memory unit 71, giving rise to a problem that the cost and size of the automatically identifying decode apparatus for reading bar codes are inevitably high and large respectively.
Addressing this problem, the present invention provides an automatically identifying decode apparatus that has a short time from reading to decoding a bar code and requires no large amount of RAM.